Recorders in the form of plotters or two-coordinate display or recording devices are frequently used as level plotters, analog computer or integrator output arrangements. Generally, there is the problematic factor of setting the recording scale which determines the recording precision achievable. Specific steps are not required for recording curves which cannot have any excessive peaks, or for curves where such peaks are not expected. However, the situation is critical if in addition to the expected curve there will be excessive peaks, or even runaways. If the recording scale is set so that practically all curve peaks are recorded with some certainty, the recording precision may be unsatisfactory and important information might be lost. Apart from the loss of data, the cutting off of excessive curve peaks and runaways may not always be advisable since a curve to be recorded may take a true measured value course over a significant distance along the margin of the recording fields, if only with a very small probability. Consequently, it is not obvious that the presented information is genuine.
Heretofore, German Patent DE-OS No. 1,798,042 provided a comparison between the measured value to be registered and a reference value corresponding to the margin of the recording field. Specific electrodes at the ends of the printing arrangement or of the recording element were energized for off-scale excursions of incoming measured values. These electrodes cause response of recording elements for marking the presence of a curve area outside the recording field on the recording medium. Although this procedure permits a clear differentiation between curve areas outside the recording field, and measured value courses along the margins of the recording field, there still is loss of information associated with curve areas outside of the recording field. Therefore, the scale setting for curve recording has to be critically considered so there is no loss of information. There exists measuring devices with maximum and minimum value recording, as shown in German Patent DE-OS No. 2,656,304, comprising counter, measured value comparing unit and storage. However, this device does not include continuous measured value recording of off-scale excursions.
It is known to provide scale factor changes for recording of results supplied by an analog computer automatically, for example, as specified in "Elektronische Analogierechenmaschinen" by G. A. Korn, and T. M. Korn, published by "Berliner Union", Stuttgart 1960, pages 386 and 387. Accordingly, an arithmetic unit can be brought into a "hold condition," either periodically or after predetermined intervals, for reading values of selected machine variables for check, print, recording medium processing, or transmission. During intervals in such procedure, scale factors can be altered, if necessary. That procedure can also be released automatically as soon as selected machine variables either fall short of or exceed predetermined values. Compare circuits are used for operating electronic switching devices which bring the analog computer into the "hold condition" and which alter the scale factor so that the calculation can be initiated with correct scale setting.
If the margins of a recording field are used as reference values, for these predetermined values to be exceeded or not reached, a suitable recording scale ensures either that excessive peaks can be recorded because with a standard curve there is a sufficient scale or that the precision in the recording of curve maxima and minima is accordingly reduced. Hence, information is also lost because of reduced resolution. It is also known, from "Electronic Analog and Hybrid Computers" by G. A. Korn and T. M. Korn, published by McGraw Hill Book Company page 38, that in connection with analog computer output the scale factor is to be determined empirically. According to pages 451 and 452 thereof, signalling lights might be used for indicating an off-scale excursion in curve recording.
The prior art does not present a suitable solution for the problem of off-scale excursions in curve recording and representation.